A South Korean nuclear reactor came to an emergency halt Thursday, its operator said, only five days after it resumed operations following a prolonged investigation to identify the cause of a shutdown seven months earlier.

The No. 3 reactor at Hanbit Nuclear Power Plant in Yeonggwang, 320 kilometers southwest of Seoul, was automatically shut down at 1:29 p.m., according to the Korea Hydro & Nuclear Power Corp.

The state-run nuclear plant operator said there was no problem with the safety of the reactor, noting that the shutdown appeared to have been caused by problems in the reactor's coolant pump.

"The reactor is currently in a stable condition with an investigation to find the exact cause of the problem now under way," KHNP said in a short text message.

However, the shutdown came less than a week after the nuclear safety commission approved the resumption of the reactor, which had been offline since automatically shutting down on Oct. 17 due to problems with its steam generator.

KHNP later found a number of what it called foreign materials in the generator, some of which could not be removed, delaying the resumption of the reactor's operation for the past seven months.

The safety commission's approval for resumption came after a weeklong test run of the reactor showed the remaining foreign objects in the steam generator posed little or no danger to the safety of the reactor. (Yonhap)